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Abstract:

Disclosed is a method of preparing a conductive polymer composition, in
which FTS (Ferric p-toluene sulfonate) is used as a dopant and mixed with
a conductive polymer monomer before polymerizing the conductive polymer
monomer, thereby facilitating the control of the concentration of the
conductive polymer composition and increasing the electrical conductivity
of the conductive polymer composition. A method of manufacturing a
conductive film is also provided.

2. The method of claim 1, wherein the FTS (Ferric p-toluene sulfonate) is
used so that a molar ratio of conductive polymer monomer to FTS is
1:0.5.about.1:3.5.

3. The method of claim 1, wherein the FTS (Ferric p-toluene sulfonate) is
used so that a molar ratio of conductive polymer monomer to FTS is
1:2.about.1:3.

4. The method of claim 1, wherein the conductive polymer monomer solution
comprises 100 parts by weight of the conductive polymer monomer,
10.about.200 parts by weight of the binder, and 5,000.about.50,000 parts
by weight of the solvent.

5. The method of claim 1, wherein the polymerizing is performed using
oxidation polymerization.

6. The method of claim 1, wherein the binder is one or more selected from
among gelatin, cellulose-, acryl-, epoxy-, ester-, urethane-, ether-,
carboxyl-, and amide-based binders.

7. The method of claim 1, wherein the conductive polymer monomer is
selected from among thiophene, aniline, pyrrole, acetylene, phenylene and
derivatives thereof.

11. The method of claim 10, wherein the FTS (Ferric p-toluene sulfonate)
is used so that a molar ratio of conductive polymer monomer to FTS is
1:0.5.about.1:3.5.

12. The method of claim 10, wherein the FTS (Ferric p-toluene sulfonate)
is used so that a molar ratio of conductive polymer monomer to FTS is
1:2.about.1:3.

13. The method of claim 10, wherein the conductive polymer monomer
solution comprises 100 parts by weight of the conductive polymer monomer,
10.about.200 parts by weight of the binder, and 5,000.about.50,000 parts
by weight of the solvent.

14. The method of claim 10, wherein the polymerizing is performed using
oxidation polymerization.

15. The method of claim 10, wherein the binder is one or more selected
from among gelatin, cellulose-, acryl-, epoxy-, ester-, urethane-,
ether-, carboxyl-, and amide-based binders.

16. The method of claim 10, wherein the conductive polymer monomer is
selected from among thiophene, aniline, pyrrole, acetylene, phenylene and
derivatives thereof.

Description:

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of Korean Patent Application
No. 10-2011-0000302, filed Jan. 3, 2011, entitled "Method of preparing
conductive polymer composition and method of manufacturing conductive
film using the same," which is hereby incorporated by reference in its
entirety into this application.

BACKGROUND OF THE INVENTION

[0002] 1. Technical Field

[0003] The present invention relates to a method of preparing a conductive
polymer composition and a method of manufacturing a conductive film using
the same.

[0004] 2. Description of the Related Art

[0005] Alongside the growth of computers using digital technology, devices
assisting computers have also been developed, and personal computers,
portable transmitters and other personal information processors are used
to process text and graphics using a variety of input devices such as
keyboards, mouse elements and so forth.

[0006] The rapid advancement of the information-based society, which is
disseminating the use of computers, is accompanied by the problem of
difficulty in efficiently operating products using only the keyboard and
the mouse to perform the functions of an input device. Accordingly, there
is increasing demand for devices which are simple and infrequently
malfunction, and which enable information to be easily input by anyone.

[0007] Furthermore, technology for input devices has surpassed the mere
level of fulfilling general functions and has progressed toward
technology related to high reliability, durability, innovation, designing
and manufacturing. To this end, touch panels have been developed as
devices capable of inputting information such as text and graphics.

[0008] The touch panel is mounted on the display surface of an image
display device such as a flat panel display including an electronic
organizer, a liquid crystal display (LCD), a plasma display panel (PDP),
an electroluminescence (El) element etc., or a cathode ray tube (CRT), so
that a user selects the information desired while looking at the image
display device.

[0009] Also, touch panels are generally classifiable as being of a
resistive type, a capacitive type, an electromagnetic type, a SAW
(Surface Acoustic Wave) type, and an infrared type. The type of touch
panel selected is one that is adapted for an electronic product in
consideration of signal amplification problems, resolution differences,
the degree of difficulty of designing and manufacturing technology,
optical properties, electrical properties, mechanical properties,
resistance to the environment, input properties, durability and economic
benefits of the touch panel. In particular, resistive touch panels and
capacitive touch panels are widely and prevalently used in different
fields.

[0010] In the case of resistive touch panels, they are configured so that
upper/lower transparent electrode films are separated from each other by
a spacer and are brought into contact with each other by pressing.
Particularly useful are digital resistive type and analog resistive type
in such a manner that when an upper conductive film having the upper
transparent electrode film is pressed by an input element such as a
finger, a pen, etc., the upper/lower transparent electrode films are
electrically connected with each other, and changes in voltage in
response to changes in resistance at the touch position are sensed by the
controller to thus recognize the touch coordinates.

[0011] In the case of capacitive touch panels, an upper conductive film
having a first transparent electrode and a lower conductive film having a
second transparent electrode are spaced apart from each other, and an
insulating material is interposed between the first transparent electrode
and the second transparent electrode so that these transparent electrodes
do not come into contact with each other. Furthermore, electrode wires
which are connected to the transparent electrodes are formed on the upper
conductive film and the lower conductive film. The electrode wires
transfer changes in capacitance occurring from the first transparent
electrode and the second transparent electrode to the controller as the
touch screen is touched by the input element.

[0012] The transparent electrodes have been conventionally formed using
ITO (Indium Tin Oxide), but thorough research into conductive polymers as
alternatives thereof is ongoing. The conductive polymers are advantageous
because of higher flexibility and a simpler coating process, compared to
ITO. Because of such advantages, the conductive polymers are receiving
attention as an important element of flexible displays corresponding to
next-generation technology, as well as the touch panels.

[0013] Among conductive polymers,
polyethylenedioxythiophene/polystyrenesulfonate (PEDOT/PSS) may exhibit
superior electrical conductivity and is thus widely commercially
available. A conductive polymer composition containing PEDOT/PSS is
prepared by polymerizing a conductive polymer monomer thus forming
PEDOT/PSS, and adding other additives such as a binder, a dispersion
stabilizer, an additional dopant, etc. However, conventional PEDOT/PSS is
disadvantageous because there is a need to adjust the concentrations of
PSS, PEDOT and a solvent in order to disperse PEDOT/PSS in water,
undesirably complicating the preparation process. Moreover, as the touch
screen, display and so on are required to be small-sized and highly
integrated, the electrical conductivity of the transparent electrode is
regarded as very important, but PEDOT/PSS is problematic because it does
not fulfill the electrical conductivity of a transparent electrode when
used in lieu of ITO.

SUMMARY OF THE INVENTION

[0014] Accordingly, the present invention has been made bearing in mind
the problems encountered in the related art and the present invention is
intended to provide a method of preparing a conductive polymer
composition, which includes polymerizing a conductive polymer monomer
using FTS (Ferric p-toluene sulfonate) as a dopant in place of PSS.

[0016] In this aspect, FTS (Ferric p-toluene sulfonate) may be used so
that a molar ratio of conductive polymer monomer to FTS is
1:0.5˜1:3.5.

[0017] Furthermore, FTS (Ferric p-toluene sulfonate) may be used so that a
molar ratio of conductive polymer monomer to FTS is 1:2˜1:3.

[0018] In this aspect, the conductive polymer monomer solution may
comprise 100 parts by weight of the conductive polymer monomer,
10˜200 parts by weight of the binder, and 5,000˜50,000 parts
by weight of the solvent.

[0019] In this aspect, polymerizing may be performed using oxidation
polymerization.

[0020] In this aspect, the binder may be one or more selected from among
gelatin, cellulose-, acryl-, epoxy-, ester-, urethane-, ether-,
carboxyl-, and amide-based binders.

[0021] In this aspect, the conductive polymer monomer may be selected from
among thiophene, aniline, pyrrole, acetylene, phenylene and derivatives
thereof.

[0022] In this aspect, the conductive polymer monomer may be
3,4-ethylenedioxythiophene (EDOT).

[0023] In this aspect, the solvent may be any one selected from among
aliphatic alcohol, aliphatic ketone, aliphatic carboxylic acid ester,
aliphatic carboxylic acid amide, aromatic hydrocarbon, aliphatic
hydrocarbon, acetonitrile, aliphatic sulfoxide, water and mixtures
thereof.

[0025] In this aspect, FTS (Ferric p-toluene sulfonate) may be used so
that a molar ratio of conductive polymer monomer to FTS is
1:0.5˜1:3.5.

[0026] Furthermore, FTS (Ferric p-toluene sulfonate) may be used so that a
molar ratio of conductive polymer monomer to FTS is 1:2˜1:3.

[0027] In this aspect, the conductive polymer monomer solution may
comprise 100 parts by weight of the conductive polymer monomer,
10˜200 parts by weight of the binder, and 5,000˜50,000 parts
by weight of the solvent.

[0028] In this aspect, polymerizing may be performed using oxidation
polymerization.

[0029] In this aspect, the binder may be one or more selected from among
gelatin, cellulose-, acryl-, epoxy-, ester-, urethane-, ether-,
carboxyl-, and amide-based binders.

[0030] In this aspect, the conductive polymer monomer may be selected from
among thiophene, aniline, pyrrole, acetylene, phenylene and derivatives
thereof.

[0031] In this aspect, the conductive polymer monomer may be
3,4-ethylenedioxythiophene (EDOT).

[0032] In this aspect, the solvent may be any one selected from among
aliphatic alcohol, aliphatic ketone, aliphatic carboxylic acid ester,
aliphatic carboxylic acid amide, aromatic hydrocarbon, aliphatic
hydrocarbon, acetonitrile, aliphatic sulfoxide, water and mixtures
thereof.

BRIEF DESCRIPTION OF THE DRAWING

[0033] FIG. 1 is a graph showing the electrical conductivity of conductive
films of Examples 1 to 4.

DESCRIPTION OF SPECIFIC EMBODIMENTS

[0034] The features and advantages of the present invention will be more
clearly understood from the following detailed description and
embodiments. Furthermore, descriptions of known techniques, even if they
are pertinent to the present invention, are considered unnecessary and
may be omitted in so far as they would make the characteristics of the
invention unclear.

[0035] Furthermore, the terms and words used in the present specification
and claims should not be interpreted as being limited to typical meanings
or dictionary definitions, but should be interpreted as having meanings
and concepts relevant to the technical scope of the present invention
based on the rule according to which an inventor can appropriately define
the concept implied by the term to best describe the method he or she
knows for carrying out the invention.

[0036] Hereinafter, embodiments of the present invention will be described
in detail

[0037] According to the present invention, a method of preparing a
conductive polymer composition includes (A) providing a conductive
polymer monomer solution comprising a conductive polymer monomer, FTS
(Ferric p-toluene sulfonate), a binder and a solvent, and (B)
polymerizing the conductive polymer monomer solution. Before polymerizing
the conductive polymer monomer, the conductive polymer monomer is mixed
with the dopant such as FTS, thus facilitating the preparation of the
conductive polymer composition possessing high electrical conductivity.
Below, the method of preparing the conductive polymer composition is
sequentially described.

[0038] Specifically, the conductive polymer monomer solution comprising
the conductive polymer monomer, the binder and the solvent which are
mixed together is first prepared. The conductive polymer monomer and the
binder are added to the solvent and then mixed using stirring and
sonification, thereby obtaining the conductive polymer monomer solution.
The components of the conductive polymer monomer solution are described
in detail.

[0039] The conductive polymer monomer is an electrically conductive
monomer having a single π-electron per carbon atom. A conductive
polymer resulting from polymerizing the conductive polymer monomer has a
molecular weight of about 10,000 or more. The conductive polymer is
advantageous because a thin film that is lighter and more flexible may be
obtained than when typically using ITO (Indium Tin Oxide) for a
transparent electrode.

[0040] The conductive polymer monomer may be selected from among
thiophene, aniline, pyrrole, acetylene, phenylene and derivatives
thereof. The conductive polymer monomer is advantageous because the
polymerization thereof is easy and electrical conductivity becomes
increased.

[0042] Used as a dopant and oxidizer, FTS (Ferric p-toluene sulfonate) is
added to the conductive polymer monomer solution. The conductive polymer
having a single π-electron per carbon atom needs a material
functioning as a charge carrier which adds or removes charges to or from
part of the π orbital function thereof so as to exhibit electrical
conductivity. Such a material is referred to as a dopant. In the case of
polystyrenesulfonate typically used as the dopant, the concentrations of
PSS, PEDOT and the solvent should be adjusted so that they are dissolved
in water, and the process of preparing a conductive polymer composition
is undesirably complicated. Whereas, because FTS in a wide concentration
range may be efficiently mixed with the solvent such as alcohol and the
conductive polymer monomer, it is easy to adjust the concentration of the
conductive polymer composition upon preparation of the conductive polymer
composition using FTS as the dopant. In the case where the conductive
polymer is prepared using FTS as the dopant, a conductive film having
high electrical conductivity as shown in the following test example may
be obtained.

[0043] Also, FTS is used as the dopant to polymerize the conductive
polymer monomer and simultaneously functions as the oxidizer, and thus
the energy level of the polymerized conductive polymer is lowered so that
electrons are easily transferred to a high energy state, thereby
increasing the electrical conductivity of the conductive polymer
composition.

[0044] The conductive polymer monomer and FTS are used at a molar ratio of
1:0.5˜1:3.5, particularly favored being 1:2˜1:3. If the molar
ratio of conductive polymer monomer to FTS is less than 1:0.5, the degree
of increasing the electrical conductivity due to the addition of FTS is
insignificant. In contrast, if the molar ratio thereof is larger than
1:3.5, there is no effect of increasing the electrical conductivity due
to the addition of FTS.

[0045] The binder is added to enhance the force of adhesion to a
substrate. The binder may be one or more selected from among gelatin,
cellulose-, acryl-, epoxy-, ester-, urethane-, ether-, carboxyl-, and
amide-based binders. These examples are merely illustrative, and the
present invention is not limited thereto.

[0046] As such, the binder is used in an amount of 10˜200 parts by
weight relative to 100 parts by weight of the conductive polymer monomer.
Particularly favored is 40˜60 parts by weight. If the amount of the
binder is less than 10 parts by weight, the degree of enhancing adhesion
is lowered. In contrast, if the amount thereof is larger than 200 parts
by weight, it is excessively increased compared to the amount of the
conductive polymer monomer, undesirably reducing the electrical
conductivity of the conductive polymer composition.

[0047] The solvent is used to disperse the conductive polymer monomer in a
solution. The solvent may include any one selected from among aliphatic
alcohol, aliphatic ketone, aliphatic carboxylic acid ester, aliphatic
carboxylic acid amide, aromatic hydrocarbon, aliphatic hydrocarbon,
acetonitrile, aliphatic sulfoxide, water, and mixtures thereof. These
examples are merely illustrative, and the present invention is not
limited thereto.

[0048] The solvent is used in an amount of 5,000˜50,000 parts by
weight, particularly favored being 7,000˜30,000 parts by weight,
relative to 100 parts by weight of the conductive polymer monomer. If the
amount of the solvent is less than 5,000 parts by weight, dispersibility
of the conductive polymer is decreased. In contrast, if the amount
thereof is larger than 50,000 parts by weight, the electrical
conductivity of the conductive polymer composition is decreased.

[0049] In the present invention, the conductive polymer monomer solution
may further include a dispersion stabilizer, a surfactant, an antifoamer,
etc.

[0050] Subsequently, the conductive polymer monomer solution thus prepared
is polymerized, thus preparing the conductive polymer composition. In the
present invention, the conductive polymer monomer is mixed with FTS in
lieu of PSS which is typically used, and is then polymerized, thus
increasing the electrical conductivity of the conductive polymer.
Furthermore, the conductive polymer composition may be easily prepared
without the need to adjust the concentrations of PSS, the conductive
polymer monomer and the solvent.

[0052] In the chemical polymerization, oxidation polymerization is adopted
so that the conductive polymer is prepared. The oxidation polymerization
is advantageous in terms of low cost and a simple polymerization process.
The oxidation polymerization is used so that a monomer is oxidized using
an oxidizer such as Lewis acid and thus polymerized into a conductive
polymer.

[0053] In addition, according to an embodiment of the present invention, a
method of manufacturing a conductive film includes (A) providing a
conductive polymer monomer solution comprising a conductive polymer
monomer, FTS (Ferric p-toluene sulfonate), a binder and a solvent, (B)
polymerizing the conductive polymer monomer solution thus preparing a
conductive polymer composition, (C) applying the conductive polymer
composition on a base member, and (D) drying the base member. The method
of manufacturing the conductive film is specified below. The description
that overlaps with the aforementioned description is omitted or simply
described.

[0055] The molar ratio of conductive polymer monomer to FTS falls in the
range of 1:0.5˜1:3.5, particularly favored being 1:2˜1:3. The
method of manufacturing the conductive film according to the present
invention is advantageous because FTS is used as the dopant in the
polymerization of the conductive polymer monomer, thus exhibiting high
electrical conductivity of the conductive film and simplifying the
manufacturing process.

[0056] Also, the conductive polymer monomer solution may be composed of
100 parts by weight of the conductive polymer monomer, 10˜200 parts
by weight of the binder, and 5,000˜50,000 parts by weight of the
solvent.

[0057] Next, the conductive polymer monomer solution is polymerized thus
preparing the conductive polymer composition. The polymerization of the
conductive polymer monomer solution is performed using oxidation
polymerization which is advantageous in terms of low cost and a simple
polymerization process.

[0058] Next, the conductive polymer composition is applied on the base
member. The conductive polymer composition may be applied by being
patterned using a dry process or a wet process. Examples of the dry
process include sputtering, evaporation, etc., and examples of the wet
process include dip coating, spin coating, roll coating, spray coating,
etc.

[0059] The base member, which is transparent, includes a glass substrate,
a film substrate, a fiber substrate, or a paper substrate. In particular,
the film substrate may be made of polyethyleneterephthalate (PET),
polymethylmethacrylate (PMMA), polypropylene (PP), polyethylene (PE),
polyethylenenaphthalene dicarboxylate (PEN), polycarbonate (PC),
polyethersulfone (PES), polyimide (PI), polyvinyl alcohol (PVA), cyclic
olefin copolymer (COC), or styrene copolymer, but the present invention
is not necessarily limited thereto.

[0060] Next, the base member coated with the conductive polymer
composition is dried. When the applied conductive polymer composition is
dried, a transparent electrode in fixed form is obtained. The drying
process is performed using hot air drying, IR drying, etc.

[0061] A better understanding of the present invention may be obtained via
the following examples which are set forth to illustrate, but are not to
be construed as limiting the present invention.

Example 1

[0062] Into a 100 ml round-bottom reactor, 0.4 mol (3 g) a solvent
n-butanol, 0.12 g of an acrylic binder, 0.422 mmol (0.06 g) a conductive
polymer monomer 3,4-ethylenedioxythiophene (EDOT), and 1.26 mmol (0.854
g) FTS (Ferric p-toluene sulfonate) in which a molar ratio of conductive
polymer monomer to FTS was 1:2.98 were added, after which 30-min stirring
and sonification were performed, thus preparing a conductive polymer
monomer solution. Thereafter, the conductive polymer monomer solution was
subjected to oxidation polymerization using an oxidizer at 25° C.
for 3 hours, thus preparing a PEDOT/FTS conductive polymer composition.
The conductive polymer composition was then applied on a base member
using spin coating and then dried in an oven at 70° C. for 30 min,
thus manufacturing a conductive film.

Example 2

[0063] A conductive polymer composition was prepared in the same manner as
in Example 1, with the exception that 0.844 mmol (0.572 g) FTS was added
so that a molar ratio of conductive polymer monomer to FTS was 1:2.

[0064] The conductive polymer composition was applied on a base member
using spin coating and then dried in an oven at 70° C. for 30 min,
thus manufacturing a conductive film.

Example 3

[0065] A conductive polymer composition was prepared in the same manner as
in Example 1, with the exception that 0.422 mmol (0.286 g) FTS was added
so that a molar ratio of conductive polymer monomer to FTS was 1:1.

[0066] The conductive polymer composition was applied on a base member
using spin coating and then dried in an oven at 70° C. for 30 min,
thus manufacturing a conductive film.

Example 4

[0067] A conductive polymer composition was prepared in the same manner as
in Example 1, with the exception that 1.477 mmol (1 g) FTS was added so
that a molar ratio of conductive polymer monomer to FTS was 1:3.5.

[0068] The conductive polymer composition was applied on a base member
using spin coating and then dried in an oven at 70° C. for 30 min,
thus manufacturing a conductive film.

Comparative Example

[0069] A conductive polymer composition was prepared in the same manner as
in Example 1, with the exception that 1.26 mmol polystyrenesulfonate
(PSS) was used as the dopant in lieu of FTS so that a molar ratio of
conductive polymer monomer to PSS was 1:2.98.

[0070] The conductive polymer composition was applied on a base member
using spin coating and then dried in an oven at 70° C. for 30 min,
thus manufacturing a conductive film.

[0071] <Test Example>

[0072] The electrical conductivity of the conductive films manufactured
from the conductive polymer compositions of Examples 1 to 4 and
Comparative Example was evaluated. The electrical conductivity was
measured using Loresta EP MCP-T360 available from Mitsubishi Chemical.
FIG. 1 is a graph showing the electrical conductivity of the conductive
films of Examples 1 to 4.

[0073] As is apparent from Table 1, when FTS was used as a dopant,
electrical conductivity was superior compared to when using PSS
(Comparative Example). Furthermore, when FTS was added at a molar ratio
of conductive polymer monomer to FTS ranging from 1:2 to 1:3, the degree
of increasing the electrical conductivity of the conductive film was the
greatest.

[0074] As described hereinbefore, the present invention provides a method
of preparing a conductive polymer composition and a method of
manufacturing a conductive film. According to the present invention, FTS
(Ferric p-toluene sulfonate) is used as a dopant and mixed with a
conductive polymer monomer before polymerizing the conductive polymer
monomer, thereby facilitating the control of the concentration of the
conductive polymer composition and increasing the electrical conductivity
of the conductive polymer composition.

[0075] Although the embodiments of the present invention regarding the
method of preparing a conductive polymer composition and the method of
manufacturing a conductive film have been disclosed for illustrative
purposes, those skilled in the art will appreciate that a variety of
different modifications, additions and substitutions are possible,
without departing from the scope and spirit of the invention as disclosed
in the accompanying claims. Accordingly, such modifications, additions
and substitutions should also be understood as falling within the scope
of the present invention.